Internal olefins have been conventionally used in various applications specifically such as base oils for oil drilling, raw materials for detergents, raw materials for sizing agents for papers, base oils or raw materials for lubricants and raw materials for chemical products.
The internal olefins used in these applications have been required to satisfy the following requirements.
For example, in the applications of base oils for oil drilling, the internal olefins having 16 and 18 carbon atoms are generally used. The internal olefins used in such applications have been required to exhibit well-controlled pour point and kinematic viscosity as well as a high biodegradability.
As the method for production of such internal olefins, there are known techniques for internal isomerization of α-olefins using a catalyst formed by supporting Pt, Ru, Ni, etc., on a carrier such as alumina and zeolite, or ferrierite as one of zeolites. These techniques have been already industrially put into practice.
In general, the internal olefins are converted into tri-substituted or tetra-substituted branched olefins when subjected to skeletal isomerization reaction. It is known that these branched olefins not only exhibit a change in properties such as drop of pour point but also are deteriorated in biodegradability in natural environments as compared to the original olefins.
In various applications of the internal olefins as described above, the drop of a pour point thereof is preferable, in particular, when used in the applications of base oils for oil drilling. On the other hand, the raw materials exhibiting a poor biodegradability are presently actually unusable in the applications having a high possibility of discharging the materials into the natural environments such as detergents and base oils for oil drilling owing to recent environmental policies for prohibiting release of such materials.
Conventionally, the following patent applications relating to the method for producing olefins usable as base oils for oil drilling, have been filed.
(1) The method of isomerizing α-olefins by using a molecular sieve containing no metal belonging to Group 8 of the Periodic Table wherein the obtained reaction product contains branched olefins in an amount of 5% by mass or more, and a content of the α-olefins in the reaction product is less than 20% by mass (for example, U.S. Pat. No. 5,965,783).
(2) The method of isomerizing α-olefins by using a molecular sieve of a non-zeolite structure having an optimum pore size wherein the raw materials contain at least 50% by mass of olefins having 12 or more carbon atoms, and the obtained reaction product contains at least 5% by mass of branched olefins (for example, U.S. Pat. No. 6,054,415).
(3) The method of isomerizing α-olefins by using a pentasil zeolite modified with a Ni monoxide wherein the obtained reaction product contains at least 90% by mass of linear olefins, and a content of branched olefins therein is less than 5% by mass (for example, U.S. Pat. No. 6,054,629).
(4) The method of isomerizing α-olefins having 4 to 50 carbon atoms by using a molecular sieve containing an aluminophosphate having one-dimensional pores wherein a branching reaction of the olefins is prevented by the one-dimensional pores (for example, U.S. Pat. No. 6,281,404).
Also, the following patent applications relating to base oils for oil drilling have been conventionally filed.
(5) A base oil for oil drilling, comprising olefins having 12 or more carbon atoms which contain linear olefins in an amount of 50 to 100% by mass and α-olefins in an amount of less than 20% by mass, an additive and water (for example, U.S. Pat. No. 5,589,442).
(6) A base oil for oil drilling, comprising olefins having 12 or more carbon atoms which contain branched olefins in an amount of 15 to 90% by mass and α-olefins in an amount of less than 20% by mass, an additive and water (for example, U.S. Pat. No. 5,741,759).
(7) A base oil for oil drilling, comprising 30% by mass or more of olefins having 12 or more carbon atoms which contain linear olefins in an amount of 50 to 100% by mass and α-olefins in an amount of less than 20% by mass, an additive and water (for example, U.S. Pat. No. 6,057,272).
However, the conventional olefins used as the above base oils for oil drilling as well as those contained in the base oils for oil drilling have failed to satisfy the requirements such as a good biodegradability when discharged into the environments, a less toxicity against marine organisms, etc., and a sufficient fluidity when used as base oils for oil drilling.
Therefore, it has been demanded to provide olefins capable of satisfying the requirements such as a good biodegradability when discharged into the environments, a less toxicity against marine organisms, etc., and a sufficient fluidity when used as base oils for oil drilling.